Ruthenium-containing materials in which the ruthenium is present in the metallic or oxidic form (ore concentrates, target materials produced by powder metallurgy from ruthenium metal and ruthenium alloys, other cementates) need to be activated for further purification operations and converted into a water-soluble form.
Various processes are known for mobilising and/or separating off ruthenium:                melt flow with KOH/KNO3 and subsequent formation of RuO4 by the oxidation of the alkaline solution with chlorine gas (JP39019951; C. Claus, J. prakt. Chem. 79 [1860] 28),        oxidation and dissolution in HCl or HNO3 with potassium chlorate as oxidising agent (F. Krauss, Z. anorg. Ch. 117 [1921] 115),        exploiting the solubility in hypochlorite solution (Howe, JACS 47 [1925] 2928),        alcohol precipitation of ruthenium from highly alkaline solution (C. Claus, J. prakt. Chem. 79 [1860] 28; L. Wöhler, Zeitschrift f. anorg. Chem. 139 [1924] 205-219),        treating ruthenate solutions in sequence with chlorate and bromate (EP 1 114 795 A1),        heating ruthenium-containing hydrochloric acid noble metal solutions and subsequent addition of chlorate and further heating of the suspension/solution formed to 80 to 90° C. and collection of the ruthenium tetroxide formed (U.S. Pat. No. 4,390,366),        Oxidation of alkali ruthenate in aqueous solutions (DE 39 35 798 A1) in the case of which the oxidation with ozone is carried out at pH values above 8. Alternatively, the ruthenium-containing noble metal solution present can be distilled with sodium chlorate and/or chlorine gas.        
Processes according to the state of the art have the following disadvantages: aqua regia or concentrated acids/chlorine gas used as oxidising agent do not dissolve ruthenium or only very slowly. Ruthenium is soluble in sodium hypochlorite liquor; however, volatile ruthenium(VIII) oxide is partly formed in this case directly. As a result, the digestion step cannot be separated from the separation step. The selenium contained in ore concentrates interferes with the purification of the noble metals in the further steps such that its rapid elimination, if possible at the beginning of the partitioning process, is desirable.